577 D2 Curve Tracer Calibration.


henasau@...
 

I received my 577 Curve Tracer last week. Very impressed, very nice instrument.
When I was bringing it up with auto-transformer tantalum cap in -30V PSU started to sizzle. Later, I found two suspect high ESR tantalum electrolytics on the main board. After replacing them I was able to test zener diodes. I was pretty close then. Still no output from the step generator though. Finally I found two sets of contacts in large relay on the main board developed high resistance. A bit more switch cleaning an the beast burst to life.

I thought I will give some performance check. I found my 577 was slightly out.
I went through all calibration procedures without to much of a problem but one got my head scratching.
Number 9 Vertical gain adjustment. I thought I followed everything according to manual but despite trying it for many times I couldn't get the results manual is expecting.

After initial setting up, manual asks to position the spot to the bottom graticule and then take the spot up with OffstMultControl until DVM reads 4V. I could only get to about center of the screen. I suspect this is half way.
Now, I don't know, perhaps I am doing something wrong or maybe there is an error in the manual. There is similar procedure for setting up horizontal gain which I had no problem with.
There is still possibility vertical amplifier is faulty but before I tear it apart I thought, I ask for forum's wisdom first.
Henryk

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